The Fabaceae in Northeastern Mexico (Subfamilies Caesalpinioideae (Excluding Tribe Mimoseae), Cercidoideae, and Detarioideae)

As part of the Fabaceae project of northeastern Mexico and based on field work, collection of botanical samples over the past 37 years, and reviewing botanical materials in national and international herbaria, the diversity of legumes of the subfamilies Caesalpinioideae (excluding tribe Mimoseae), Cercidoideae, and Detarioideae in northeastern Mexico has been recorded. New nomenclatural changes in tribes and genera of the subfamily Caesalpinioideae found in the new scientific bibliography are included. The subfamily Caesalpinioideae (excluding the tribe Mimoseae) includes five tribes: tribe Caesalpinieae, with eight genera (Caesalpinia, Coulteria, Denisophytum, Erythrostemon, Guilandina, Hoffmannseggia, Haematoxylum, and Pomaria) and 21 species; tribe Cassieae with three genera (Cassia, Chamaecrita, and Senna) and 28 species; tribe Ceratonieae with one genus (Ceratonia) and 1 species; tribe Gleditsieae with one genus (Gleditsia) and 1 species. The subfamily Cercidoideae includes two genera (Bauhinia and Cercis) and eight species, and the subfamily Detarioideae includes only one genus and one species (Tamarindus indicus). The total flora of these three subfamilies comprises 18 genera and 63 species, including 56 native species and 7 exotic ones: Bauhinia variegata, Cassia fistula, Ceratonia siliqua, Delonix regia, Erythrostemon gilliesii, Senna alata, and Tamarindus indicus. Endemism includes a total of 22 species and nine infraspecific categories.


Introduction
The Fabaceae rank third in species diversification worldwide, comprising 770 genera and 19,581 species [1].This family has had radical changes in its classification [2][3][4][5].This has allowed us to recognize natural and homogeneous monophyletic groups of taxa and increase the number of subfamilies from three to six: Caesalpinioideae, Cercidoideae, Detarioideae, Dialioideae, Duparquetioideae, and Papilionoideae [1].Based on the new concept of subfamilies, these are formed as follows.The subfamily Caesalpinioideae is composed of 11 tribes, 163 genera, and 4680 species [5].The subfamily Cercidoideae is composed of 12 genera and 335 species [1]; the subfamily Detarioideae includes 84 genera and 760 species [1]; the subfamily Dialioideae includes 17 genera and 85 species [1]; and the subfamily Papilionoideae includes 503 genera and almost 14,000 species [1].The subfamily Caesalpinioideae is the one that has had the greatest number of taxonomic modifications [4][5][6][7][8].The most significant taxonomic changes within the current subfamily Caesalpinioideae are the inclusion of the subfamily Mimosoideae as a tribe within this [4,5], the subtribes Dialiinae and Duparquetiinae belonging to the tribe Cassieae [8] are now recognized as two different subfamilies, Dailioideae and Duparquetioideae, respectively [1].
The subfamily Cercidoideae is distinguished by its simple, entire or bilobed, or bifoliolate leaves.The subfamily Detarioideae is recognized by its extra-floral glands located on the edges of the leaflets abaxially.The inflorescences of the subfamily Caesalpinioideae have spiral anthotaxy, commonly with paripinnate leaves, and the seeds usually have open or closed pleurogram on each of the two sides.
The Fabaceae is one of the most economically important groups of plants in the world.This importance is due to the multiple uses that humanity has given them over time, such as carbon sequestration, reduction in greenhouse gas emissions, biodiversity conservation, diversification of livestock diets, flowers for pollinators, and shade for livestock [9][10][11][12].At least 150 species of food and forage legumes have been recorded [13].Among the most important species for human consumption, Vigna, Phaseolus, Cicer, Pisum, and Lens stand out [14].Among the forage species most recognized for their economic importance at a global level are several species of Trifolium, Medicago, and Lotus [12,15].Many legume species are capable of fixing atmospheric nitrogen in association with bacteria (Rhizobium and other genera), increasing its availability in the soil [16] and ensuring nutrient cycling for better plant growth for agricultural activities [17].Legumes are also used for timber, firewood, and ornamental purposes [18]; species of the genera Peltophorum, Dalbergia, and Sesbania are used as timber; and species of the genera Bauhinia, Delonix, and Cassia are frequently used as ornamental [19].Some species of legumes produce phytosterols, steroids found in plants similar to cholesterol and are part of the components of cell membranes [20]; Tamarindus indica seed oils are rich in phytosterols [21], including phytosterols in the diet can reduce blood cholesterol, decreasing the risk of cardiovascular diseases [20].Many species of legumes are a source of food for humans, such as the leaves of Acacia auriculiformis and A. concinna, flowers of Cassia fistula, seeds of Acacia concinna and Senegalia catechu, and the pulp of Vachellia nilotica [18].From a legume species conservation perspective, pollinators and legumes are interdependent; the legumes provide key forage and depend on insect pollination for reproduction and maintenance of genetic diversity [22].Therefore, increasing legumes in intensive agricultural systems could be key to mitigating the decline of pollinators [23].Legumes are present in practically all plant communities in Mexico [24], and a large number of uses of these species have been recorded from the nutritional, environmental, manufacturing of materials, fuel, medicinal purposes, and fodder point of view [25].Among the most important uses are timber (Neltuma, Ebenopsis, Havardia, Senegalia, and Vachellia), food (Phaseolus, Lens, Tamarindus, and Cicer), medicinal purposes (Eysenhardtia and Indigofera), forage (Medicago, Vachellia, Neltuma and Leucaena), artisanal (Ebenopsis), green manure (Leucaena), fuel (Neltuma, Vachellia, Senegalia, Havardia and Ebenopsis), and charcoal (Neltuma and Vachellia) [26][27][28][29].Several species, such as Enteroloboium cyclocarpum, Neltuma juliflora, Lonchocarpus castilloi, and Dalbergia granadillo, are used as timber, furniture, bars for train tracks, wooden floors, and guitars [30].Olneya tesota is considered a high ecological value species [31], also used for medicinal purposes, food, artisanal, and hand tools [32,33].Parkinsonia praecox is widely used as food and for medicinal purposes [34]; it is used for forage, fuel, and medicinal purposes [35].Species of Canavalia, Crotalaria, Glycine, and Lupinus are used as a source of healthy products and human food [36][37][38][39].Lablab, Lathyrus, and Medicago are widely used as a source of forage, green manure, industrial, medicinal purposes, ornamental, nitrogen fixer, and food [40][41][42].The genus Phaseolus has represented one of the most important food legumes for human consumption [43].Erythrina species provide high-quality protein and alkaloids [38].Tamarindus is frequently used as a condiment [7] and to make flavored and sweet drinks [28].
Based on the nomenclatural changes of the new classification of Fabaceae [1,4,5] and given the lack of a complete study of the species richness of these three subfamilies in northeastern Mexico, the aims of this study are to provide a study of the diversity of this family and three of the subfamilies, Caesalpinioideae (excluding tribe Mimoseae, see [11]), Cercidoideae, and Detarioideae in northeastern Mexico, adding information concerning their new recently published nomenclature [1,4,5], ecology, uses, and distribution of all taxa.

Endemism
Table 2 shows the subfamilies, genera, and species of the family Fabaceae and subfamilies Caesalpinioideae and Cercidoideae with endemism in Mexico.Flowers in racemes or panicles, rarely solitary, usually bisexual, less commonly unisexual and sterile flowers, actinomorphic or zygomorphic.Sepals 3-8, free or united, valvate or imbricate, rarely absent.Petals 3-8, free or fused, rarely absent, aestivation imbricate, sometimes valvate, with the adaxial petal the innermost.Stamens 3-10 free, homomorphic or heteromorphic.Staminodes present or absent present.Filaments are free, anthers longitudinally dehiscent or through terminal pores.One ovary with many ovulate.Fruit is a pod, one to many seeds, chartaceous or thick and woody, samariform, lomentiform, craspediform, dehiscent inherently or explosively or indehiscent.
The subfamily Caesalpinioideae groups 163 genera and almost 4680 species [4], distributed in tropical, subtropical, and xeric regions of the world, and some species reach temperate areas.
Tribes of the subfamily Caesalpinioideae, excluding morphological characters of the tribe Mimoseae (see [11]), which occur in Northeastern Mexico.Fruit flattened, membranous, papery, chartaceous to woody, indehiscent or dehiscent, the valves curl up when opening, pubescent and/or with glandular, plumose, dendritic or palmate trichomes and sessile black to orange glands, unarmed or provided with spines.
Representative examined material: Tamaulipas: Shrubs or trees up to 5 m tall, armed with curved or straight prickles.Leaves bipinnate.Stipels spinose arises in the insertion of pinnae on the leaf rachis and occasionally arises at the base of leaflets.Pinnae 1-6 pairs per leaf.Leaflets 2-11 pairs per pinna.Flowers in axillary or terminal racemes, yellow, bisexual, zygomorphic.Calyx 5-lobed, the lower one marginally entire, cucullate.Petals free, the banner with red tones in the center.Stamens 10, free, hairy.Fruit flattened, coriaceous, explosively dehiscent, valves twisted after dehiscence.
Genus of 8 species of North and South America, Madagascar, and Africa [5], almost similar to Caesalpinia; the only striking difference between them is the color of flowers, which is more variable in Caesalpinia (orange, red, green, and white).
Representative examined material: Coahuila: Type: Guilandina bonduc L., Sp.Pl. 1: 381.1753.Monoecious climbers, lianas, or trailing shrubs armed with prickles, commonly forming dense colonies.Stems and branches are armed with curved spines and a pair of spines below the leaf base.Leaves bipinnate, with a pair of prickles in the insertion of pinnae and leaflets.Flowers in supra or distal racemes, yellow, unisexual; female ones staminate but sterile, and the male ones have no functional pistil.Sepals valvate, the lower one cucullate.Petals 5, similar or longer than sepals.Stamens 10, free, basally hairy.Fruit oblong to elliptic, swollen, frequently armed with spines.Seeds 1-4, subspherical to obovoid, orange, gray to brown, shiny.
Genus not fully studied is its taxonomy, still with an indeterminate number of species, up to 20 [4], with pantropical distribution, the species are widely distributed in Asia, Indo-China, Japan, South Africa, Central America, the Caribbean region, Madagascar, and Australia.
Only Shrubs or trees up to 13 m tall.Branches armed, the spines straight and triangular.Leaves pinnate (in northeastern Mexico).Leaflets 2-6 pairs per leaf, obovate, when bipinnate (very rarely so) leaves, pinnae 1-3 pairs per leaf plus one terminal pinnae.Leaflets 2-6 pairs per pinna.Flowers in axillary or distal racemes or panicles, yellow, light-yellow to white, bisexual.Calyx 5-merous, the lower sepal cucullate and slightly covering the other 4 sepals in bud.Corolla of 5 petals.Stamens 10, free, the filaments hairy in the lower half.Fruit flattened, chartaceous to membranaceous, dehiscing along the middle of the valves or near the margin, never along the sutures.Seeds 1-3, flattened.
Genus of five species, four in the tropics of America and one endemic to Namibia [59], in semi-deciduous woods, dry tropical scrublands, thorn scrub, and riparian areas.
Haematoxylum   Herbaceous, subshrubs or shrubs, pubescent, stems and leaves with orange or black sessile glands and dendroid (multicellular projections consisting of a vertical axis with plumose projections radiating off the main axis or at the tip) or palmate (similar to the dendroid ones but projections radiating mainly at the tip).Pinnae 1-7 pairs per leaf, plus one terminal.Leaflets 2-10 pairs per pinna, with sessile glands abaxially.Flowers in axillary or terminal racemes, yellow-light or bright-yellow.Sepals of different sizes, the lower one the largest, containing inside the stamens and pistil.The innermost petal (banner), erect and upper, with trichomes and stipitate-glandular trichomes dorsally, the 2 adjacent lateral petals are unguiculate, yellow, and dyed red basally.Ten stamens.Fruit oblong, falcate lunate to trapezoidal, with fluffy to stellate pubescence and glands, dehiscent, the valves coiling spirally after dehiscence.
Tribe is composed of three genera, Gleditsia, Gymnocladus, and Amtiza, and 20 species [61] distributed in temperate and subtropical areas of North and South America, Asia, and South Africa.Only one genus and one species recorded in northeastern Mexico, Gleditsia triacanthos.
Shrubs or trees, commonly dioecious, deciduous.Trunks and branches are sometimes armed with thorns, simple or branched.Branches are flexouse.Leaves alternate or apparently fasciculated, pinnate, or bipinnate.Leaflets with entire or crenate margin.Flowers axillary, in racemes or panicles, unisexual, with separate sexes or polygamous.Staminate inflorescences with abundant congested flowers.Calyx 3-5-merous.Petals as many as the teeth of the calyx, greenish or light yellow, inserted on the margin of the throat.Pistillate flowers with 4-10 staminodes and abortive anthers.Fruit elliptical, compressed, leathery, indehiscent or dehiscent, septate or continuous.red-orange.Calyx gamosepalous, 5-lobed, equal or half the length of the petals.Corolla with 5 petals, unguiculate, reflexed with age.Stamens 10, free, exert, filaments of different sizes, hairy.Fruit pendulous, broadly linear, sometimes greater than 50 cm, flattened, long, woody, septate between the seeds, persistent, dehiscent or indehiscent.Seeds elliptical.
Genus are represented by 11 species, nine of which are endemic to Madagascar, and also in Africa, Arabia, and India [4] Comments: In northeastern Delonix regia, known as framboyán or flamboyán, it is widely used as an ornamental species in public and private gardens; its fruits are called "sonajas" (rattles) and used as musical instruments.
Type: Parkinsonia aculeata L., Sp.Pl. 1: 375.1753.Shrubs or trees up to 15 m tall.Bark green.Branches are armed with two types of thorns, ones short, due to modification of the stipules, and the other ones long, due to modification of petiole and rachis.Leaves with the rachis long and dorsoventrally flattened or cylindrical and short, fasciculate, or alternate.Pinnae 1-3 pairs per leaf.Leaflets are few or numerous, generally deciduous.Flowers are axillary and solitary, in racemes or corymbs, zygomorphic, yellow.Calyx campanulate, 5-merous, yellowish.Corolla has 5 petals, is free, and sometimes the banner has reddish tones.Stamens 10, free.Fruit oblong, linear-oblong, flattened, cylindrical, or torulous, constricted between the interseminal spaces.
A genus of 11-12 species [4], from the central USA, through Mexico, Venezuela, Ecuador to Argentina, and also in Africa.In northeastern Mexico, two species were recorded.Distinguishing features: Branches armed with spines.Stipules are spinescent and located at both sides of the spinescent rachis.Leaves bipinnate (resembling two simple pinnate leaves).Pinnae 1 pair per leaf, each pinnae originating from a short rachis transformed into a spine, leaf rachis flattened.Leaflets are numerous and caducous.Pedicels articulated.Fruit 5-14 × 0.7-0.9cm, cylindrical, constricted between seeds, longitudinally striated.
Representative examined material: Coahuila:  Comments: Found in Tamaulipan thornscrub, sandy and stony soils.Also found in southern Texas.Easily differentiated from the var.macra by its lower size and pubescent ovary.
Tribe with 7 genera with pantropical distribution, extending to arid and temperate areas [65].Three genera are recorded in northeastern Mexico: Cassia, Chamaecrista, and Senna.

1A.
Filaments of 3 stamens sigmoid, several times larger than their anthers, the remaining 7 filaments straight and shorter; pedicels 2-bracteolate at or just above base; fruit indehiscent

1B.
Filaments of all stamens straight or curved, shorter or less than 2 times the length of their anthers; pedicels ebracteate or 2-bracteate, the bracteoles inserted in the middle portion or distally; fruit dehiscent or indehiscent Trees or shrubs.Leaflets, small or large.Flowers in terminal or axillary racemes, yellow.Pedicels bi-bracteolate at or just above the base.The banner is of a different color than the rest of the petals.Ten stamens, heteromorphic, three of them with their filaments proximally sigmoid and curved distally, frequently dilated in the external or distal curvature.The remaining seven stamens are smaller, without sigmoid filaments; six of these are fertile, and the remaining one is a staminode.Ovary stipitate.Fruit indehiscent, pendulous, linear, cylindrical or laterally compressed, woody, internally septate.
A genus of 30 species, circumtropical.Thirteen species in America, 12 of them in the Amazon region; one species endemic to Mexico [4]; and the rest in Africa, Madagascar, Thailand, India, Myanmar, and Australia.
Cassia fistula L., Sp.Pl.A genus of 330 species in tropical and subtropical areas.Most of the species (266) are in America, with greater diversification in South America [4], 36 in Africa, and 12 native to Australia.Comments: Used as ornamental in Mexico.It is common to prepare refreshing drinks.Probably native to Africa, but it is cultivated in many parts of the world today.

Discussion
The family Fabaceae is present throughout the entire surface of Mexico; however, its diversity is more abundant in southern Mexico, especially in the tropical zones [69].However, the diversity of legumes with an affinity for arid climates is more abundant in northeastern Mexico; this is undoubtedly due to the climate of the region, which is predominantly semiarid.Several genera, such as Senna and Chamaecrista, present a rich diversity in northeastern Mexico since almost 30% of all Mexican species of both genera are distributed in this region.Twenty-five percent of Bauhinia species are distributed in northeastern Mexico.Twenty-five percent of the Bauhinia species in Mexico are distributed in the northeast region of the country.Half of the Erythrostemon species recorded for Mexico have affinities for semi-arid climates, but there are also genera such as Hoffmansseggia and Pomaria, where more than 50% of the species present in Mexico are distributed in the northeast region and can be considered genera whose species have arid-thermophilous affinities.Of the three subfamilies of Fabaceae studied in northeastern Mexico, Caesalpinioideae is the most diversified, followed by Cercidoideae and Detarioideae.The subfamily Caesalpinioideae is abundant in tropical biomes, and most species are distributed below 2500 m elevation [4,7,52].This same distribution and ecological behavior pattern, concerning altitude, is repeated in the northeast of Mexico; the diversity of species of Caesalpinioideae is distributed in practically almost all the ecosystems of this region, mainly in semiarid and subtropical areas, while Cercioideae and Detarioideae are most frequent in subtropical climates in low plains.The tribe Caesalpinieae incorporates new segregated genera of Caesalpinia for northeastern Mexico, such as Coulteria, Denisophytum, Erythrostemon, and Guilandina [5].The new taxonomic modifications in Caesalpinioideae [4,5] also altered the number of species in the old and the new segregated genera.This is the case of Caesalpinia, with approximately 20 species in northern Mexico, where 19 of them have now been transferred to the new genera or to others such as Conzattia [5], Coulteria [5], Denisophytum [5], Erythrostemon [4,5], Guilandina [5], Hoffmannseggia [5,59], and Pomaria [5,60].Of the total species recorded for the three subfamilies, 88% are native, and 12% are exotic in northeastern Mexico; all of these exotic species are shrubs or trees.The predominant biological forms of the 71 taxa of Fabaceae recorded in northeastern Mexico are almost equally distributed; the herbaceous total 31 taxa, while the shrubs and trees add up to 40 taxa.However, ecologically, shrubs and trees play a predominant role in the vegetation of northeastern Mexico, where those are often the dominant elements of the landscape [69,70].Of the 63 species of Fabaceae recorded in northeastern Mexico, 22 of them are endemic to Mexico and the state of Texas, USA.Only 11% of the recorded Fabaceae species are endemic to northeastern Mexico.The genera with the highest number of endemism in northeastern Mexico are Bauhinia and Pomaria.Only Bauhinia bartlettii and Senna guatemalensis var.calcarea are endemic to one state, Tamaulipas.In northeastern Mexico, Haematoxylum has only been recorded with pinnate leaves.Conzattia arborea has been reported for the state of Tamaulipas, but no records of this species were found by the authors, nor in SEINet databases or any national or foreign herbaria mentioned above, so this species is not included in this study.

Study Area
Northeast Mexico is represented by the states of Tamaulipas (80,249 Km 2 ), Nuevo Léon (64,156 Km 2 ), and Coahuila (151,595 Km 2 ) (Figure 4).Within this surface are three large physiographic provinces: the Eastern Sierra Madre, the Northern Gulf Coastal Plain, and the Great North American Plain.In northeastern, contrasting changes in vegetation are the result of the variability in soil, relief, and climate [70].The variability in soils is due to their physical and chemical properties [70].; likewise, the climate is varied along the altitudinal gradient [71]..Among the most common types are tropical, dry, temperate, and cold [71,72] The altitudinal gradient in northeastern Mexico consists of low plains (0-150 m altitude), low hills (200-600 m), steep mountains (900-1600 m), high plains (1400-1800 m), and high peaks (3600 m) [72].This rich physiographic, climatic, and edaphic variability has evident effects on the structure, composition, and diversity of vegetation, and six of the nine main vegetation types of Mexico are present in this region: xeric scrub, low deciduous forest, evergreen tropical forest, mountain cloud forest, grasslands, oak forest, oak-pine forest, coniferous forest, and subalpine meadow [24,71].The Fabaceae is one of the three groups of plants best represented in Mexico [73].It is distributed in all plant communities in northeastern Mexico, being the most ecologically important element in the landscape [19,72].The aim of this study is to establish the diversity of legumes of the subfamilies Caesalpinioideae (excluding tribe Mimoseae), Cercidoideae, and Detarioideae distributed in the different environments of northeastern Mexico.
Similar to our previous work on this family of plants in northeastern Mexico [11], this study consisted of two phases; The first one was to capture in a database all the genera and species of Fabaceae, subfamilies Caesalpinioideae, Cercidoideae, and Detarioideae recorded in the scientific bibliography for northeastern Mexico.The database was expanded with the personal species records of each of the authors in the study area.In order to complement the entire diversity of this family, botanical specimens from the national herbaria were included: ANSM, CFNL, MEXU, and UAT.The second phase consisted of finding records of legume species from northeastern Mexico in foreign herbaria (CAS, MICH, NY, TX-LL, US).The databases and high-resolution digital photographs of these The variability in soils is due to their physical and chemical properties [70]; likewise, the climate is varied along the altitudinal gradient [71].Among the most common types are tropical, dry, temperate, and cold [71,72] The altitudinal gradient in northeastern Mexico consists of low plains (0-150 m altitude), low hills (200-600 m), steep mountains (900-1600 m), high plains (1400-1800 m), and high peaks (3600 m) [72].This rich physiographic, climatic, and edaphic variability has evident effects on the structure, composition, and diversity of vegetation, and six of the nine main vegetation types of Mexico are present in this region: xeric scrub, low deciduous forest, evergreen tropical forest, mountain cloud forest, grasslands, oak forest, oak-pine forest, coniferous forest, and subalpine meadow [24,71].The Fabaceae is one of the three groups of plants best represented in Mexico [73].It is distributed in all plant communities in northeastern Mexico, being the most ecologically important element in the landscape [19,72].The aim of this study is to establish the diversity of legumes of the subfamilies Caesalpinioideae (excluding tribe Mimoseae), Cercidoideae, and Detarioideae distributed in the different environments of northeastern Mexico.
Similar to our previous work on this family of plants in northeastern Mexico [11], this study consisted of two phases; The first one was to capture in a database all the genera and species of Fabaceae, subfamilies Caesalpinioideae, Cercidoideae, and Detarioideae recorded in the scientific bibliography for northeastern Mexico.The database was expanded with the personal species records of each of the authors in the study area.In order to complement the entire diversity of this family, botanical specimens from the national herbaria were included: ANSM, CFNL, MEXU, and UAT.The second phase consisted of finding records of legume species from northeastern Mexico in foreign herbaria (CAS, MICH, NY, TX-LL, US).The databases and high-resolution digital photographs of these herbaria were used as well.The databases of digital images of type specimens from the JSTOR Global Plants database were consulted and recorded.The Tropicos [74] platform database, the book Order out of Chaos [75], and the study of Hoffmansseggia [76] were consulted to query the designation of lectotypes.In the representative material examined, the symbol "!" indicates that the type specimen for the species was observed by the authors.The accepted scientific names follow WFO (World Flora Online) [77].
To differentiate the subfamilies, tribes, genera, and species of the Fabaceae, different dichotomous keys were created: (1) to differentiate the three studied subfamilies; (2) to separate the tribes within the subfamily (when necessary); (3) to differentiate the genera within each subfamily or tribe; and (4) to separate species within each genus.These keys include the main morphological characters useful for differentiating groups.Measurements of morphological structures were carried out by the authors; when the specimen was not available, measurements were obtained from the literature.
We include the currently accepted name for the species [76].In addition, the type species for each of the genera and the type specimen for each of the species are incorporated.The synonymy of each of the genera and the species (basionyms, homonyms, and heteronyms) is also contained.As a fundamental part of the species, a morphological description of each subfamily, tribe, genera, species, and infraspecific category was added; it contains the distinctive characters and some of the most characteristic morphology for their recognition.At the end of each description, a comments section is added in order to provide information regarding its global, regional, or endemic distribution, ecology, and uses.The subfamilies, tribes, genera, and species are arranged alphabetically.

Funding:
The authors received no specific funding for this work.

Table 1 .
Number of species per genus of the three subfamilies in northeastern Mexico compared to Mexico and the world.

Table 1 .
Number of species per genus of the three subfamilies in northeastern Mexico compared to Mexico and the world.

Table 2 .
Endemism of the subfamilies Caesalpinioideae and Cercidoideaeeae in northeastern Mexico.
Leaves pinnate or bipinnate, ending in a single pinnae or in a pair of pinnae.One pinnae has several pairs per leaf.Flowers are yellow, orange, red, scarlet-red, white, pink or green, bisexual or unisexual.Calyx is imbricate, the sepals are pubescent or glandular pectinate, and the lower lobe is different from the rest of the lobes, modified into a cap-shaped in the bud stage.Ten stamens, where the filaments are usually pubescent and glandular basally.
Endemic to Mexico.Recorded only in the state of Tamaulipas, in piedmont scrub, 300 (Sierra de San Carlos)-800 m altitude (Municipality of Abasolo), outside the area, in San Luis Potosi, Guanajuato, Querétaro, Guerrero, Sinaloa, Oaxaca, and Hidalgo.
Flowers are strongly asymmetrical, with one petal abaxial, opposite the pistil displaced, not centric, modified in shape (obliquely dilated) and texture, its claw commonly shorter and thicker than that of the other petals.